According to the present invention, a ball valve assembly is provided that utilizes a one-piece ball and shaft yet is simple to construct, the housing components thereof preferably being formed by casting, is economical to construct, avoids the problems associated with center split body gaskets, and allows the utilization of the screwed-in bushing for the shaft, which has advantages with respect to ease of assembly and construction.
Valves having one-piece ball and shaft arrangements are advantageous since backlash and dead band do not occur when trying to position the ball accurately for use as a flow control valve, since there is never any possibility of a dead space in a joint, as can occur with a separate ball and shaft arrangement. Also, a one-piece ball and shaft may be coated with corrosion resistent plastic or metal without risk of damage to the coating when torque is applied, the ball can be electrically grounded effectively by grounding the shaft outside the valve, the ball can--from outside the valve--be pushed into engagement with the valve seats inside the valve by imparting a side push on the shaft in the opposite direction using the shaft as a lever, and the ball is prevented from vibrating inside the valve due to flow turbulence.
In the past, there have been proposals for constructing valves having an integral ball and stem utilizing a center split body, such as shown in Canadian Pat. No. 978,172. However, such an arrangement has the disadvantage in that the body gasket is split at the shaft packing area. There have been other proposals, such as shown in U.S. Pat. Nos. 3,635,439 and 3,951,380, that avoid the problem of a center split body, however, because of the difficulties inherent in constructing side split bodies that allow the insertion of an integral ball and shaft, the type of bushings utilizable with such assemblies have been limited, and the configurations of the structure have not lent themselves to simple forms of construction, such as casting.
According to the present invention, a ball valve assembly having a one-piece ball and shaft is provided that does not have a center split body, yet may utilize simple screw-in bushings, and may be readily assembled using cast housing components. The invention also relates to a method of construction of such a ball valve assembly having a one-piece ball and shaft.
The ball valve assembly according to the present invention comprises a one-piece ball and shaft, the ball having a flattened portion adjacent the shaft and having a through bore. A valve housing comprises a body and an end cap. The body defines a central chamber and has a flow port at a first end thereof and defines an opening at a second end thereof substantially larger than the flow port. The end cap cooperates with the body second end at a second end thereof, and defines a flow port at a first end thereof. Means are provided for attaching the body and the end cap together in sealing relationship so that fluid may flow through the fluid ports. Means defining an elongated passageway in the body are also provided, the passageway for receipt of the shaft, and in one variation the defining means including a threaded wall portion including a relatively thick wall portion toward the body first end and a relatively thin wall portion toward the body second end, threads extending on the relatively thick wall portion past the termination of the relatively thin wall portion in the direction of elongation of the passageway. In another variation, the passageway is smooth and the bushing is bolted onto the body. The first sealing means, associated with the body, are provided encircling the body fluid port for cooperation with the ball, and second sealing means, associated with the end cap, are provided encircling the end cap fluid port for cooperation with the ball. The opening in the second end of the body is large enough to allow passage of the one-piece ball and stem therethrough so that the stem can pass through the passageway and the ball seated in cooperation with the first sealing means. Also, bushing means are provided for cooperating with the threaded or bored passageway of the body, and supporting and sealing the shaft. A scallop may be formed in the relatively thin wall portion and extending substantially perpendicular to the direction of elongation of the passageway to facilitate insertion of the one-piece ball and stem, the scallop being easily formable during casting, or by machining.
Where deadly poisons and the like are to be valved an all-welded valve is provided. Thin sections are provided at all interfaces between the end cap and the body, and light sealing welded joints are provided at all interfaces between the end cap and the body, as well as between thin sections of the bushing and the body. Bolts extending between flange portions of the end cap and body also may be provided to take the body stresses so that the weld is not stressed. In situations where poisonous fluids are not to be valved, the weld attaching means may be replaced by sealing rings in contact with particularly shaped portions of the body and end cap.
The present invention also contemplates a method of construction of a ball valve that is simple yet may utilize a one-piece ball and shaft. The method includes the steps of forming a one-piece ball and shaft, casting a valve housing body, forming an end cap, and forming a bushing. The valve housing body so cast has a flow port at a first end thereof and an opening at a second end thereof, and is adapted to receive sealing means encircling the flow port for cooperation with the ball; an elongated passageway for receipt of the shaft, the passageway being threaded in a relatively thick wall portion defining the passageway toward the first end of the body, and a relatively thin wall portion defining the passageway toward the second end of the body, threads extending on the thick wall portion past the termination of the thin wall portion in the direction of elongation of the passageway; and a scallop formed in the thin wall portion extending substantially perpendicular to the direction of elongation of the passageway. The end cap formed cooperates with the body second end at a second end thereof, and defines a flow port at a first end thereof, and is adapted to receive sealing means encircling the flow port for cooperation with the ball. The bushing has exterior threads corresponding to the threads in the body passageway. The method includes the further steps of inserting the shaft through the body opening and through the scallop to and through the passageway, and then moving the ball so that it is in sealing relationship with sealing means in the body, bringing the end cap into cooperative relationship with the body while simultaneously bringing end cap sealing means into sealing engagement with the ball, attaching the end cap and body together in sealing relationship, and screwing the bushing into operative association with the body passageway threads, for supporting and sealing the shaft.
The method according to the invention also may include practicing the casting and end cap forming steps so as to form thin sections of the body around the periphery of the second end thereof, and of the end cap around the periphery of the second end thereof, and by accomplishing the attaching step by welding the thin sections along all the interfaces between the body and the end cap together. Similarly, a thin section may be formed around a top peripheral portion of the bushing, and the thin section welded to the body. Flanges may be formed on the body and the end cap, and bolts passed through openings in the flanges to take the body stresses between the body and end cap so that the welds will not be stressed.
It is the primary object of the present invention to provide a simple and efficient ball valve assembly, and method of construction thereof. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.